Sum of a G.P. series is represented by the formula, Sn = a\(\frac{r^n -1}{r-1}\) , when r ≠ 1.
‘Sn’ represents the sum of the G.P. series up to nth terms,
‘a’ represents the first term,
‘r’ represents the common ratio and
‘n’ represents the number of terms.
Here,
a = x3
r = (ratio between the n term and n-1 term) x5 \(\div\) x3 = x2
n terms